'use strict';
var single_element = function(collection){
    var arr=[];
    var result=[];
    for(let i=0;i<collection.length;i++){
        if(i%2!=0){
          arr.push(collection[i]);
        }
    }
    console.log(arr);
    for(let item of arr){
        if(arr.indexOf(item)==arr.lastIndexOf(item)){
          result.push(item);
        }
        else{
        }
    }
    console.log(result);
    return result;
};
module.exports = single_element;
// var collection_b = [11, 11, 22, 11, 33, 11];
// console.log(single_element(collection_b));